Coil-type electrical connector



March 2, 1965 J. s. ZDANIS 3,171,705

COIL-TYPE ELECTRICAL CONNECTOR Original Filed April 25, 1962 2 heet -Sheet l 26 FIG. 7 F/6.8 INVENTOR 4 JOHN s. ZDAN/S March 1965 J. s. ZDANIS COIL-TYPE ELECTRICAL CONNECTOR 2 Sheets-Sheet 2 Original Filed April 25, 1962 INVENTOR JOHN S. ZDANIS United States Patent 3,171,705 COIL-TYPE ELECTRICAL CONNECTOR John S. Zdanis, Watertown, Conn., assignor to The Siemon Company Original application Apr. 25, 1%2, Ser. No. 190,173. Divided and this application June 5, 1963, Ser. No. 285,728

2 Claims. (Cl. 339-97) This invention relates to electrical connectors and more particularly to electrical connectors embedded in a terminal connecting block.

Terminal connecting blocks are used extensively in the wire communications industry to provide a convenient and orderly means of making mass wire terminations. For example, they are used by the telephone industry in distribution cabinets for connecting conductors in a cable from an exchange to other conductors extending to various stations within a building or to other limited areas of service. Such connecting blocks must be constructed to allow ready connection of new subscribers and the disconnection of subscribers whose service is terminated. Therefore, solderless connections are generally used.

Soldcrless connections depend on pressure or stress exerted by the connecting apparatus on the conductors to insure intimate electrical contact and to hold the conductors in place. Many types of so-lderless connections are known; such as, for example, sockets or plugs wherein a male element is inserted into a female element. One of the most common types of solderless connections used in terminal connecting blocks such as are used by the telephone industry is the screw connection. This may comprise a base of insulating material in which there are embedded a plurality of threaded terminals or posts, each post being provided with a nut. The terminals are generally arranged in two parallel rows. A connection of a conductor coming from the exchange with a conductor or conductors going to the individual subscribers may be made on a single post by wrapping the conductors around the post and then tightening the nut. On the other hand, the terminals in one of the parallel rows may be connected to the incoming conductor from the exchange and the terminals in the other row may be connected to the conductors going to the subscribers. Connections between the two rows of terminals may be made, for example, by means of bridging wires. To use this type of terminal connecting block, it is necessary to strip the insulation from the ends of the conductors, wrap them around the post and then tighten the nut to insure good contact and to hold the conductors in place. This type of terminal connecting block is subject to several disadvantages. In addition to the fact that the insulation must be manually stripped from the end of the conductor before it is connected to a terminal, it has been found that the pressure of the nut pressing down on the stud which is resisted by the upward thrust of the stud, results in metal fatigue, especially in the threads of the stud; and, after a period of time, results in a poor contact with the connector. Moreover, only a limited number of connections can be made effectively at any one terminal post. Furthermore, when the connecting block is subjected to sustained periods of vibration, the nuts have a tendency to become loose and contact with the conductors may be lost.

It is an object of this invention to provide an electrical connector which automatically strips the insulation from the conductor and makes the required contact. It is another object of this invention to provide a terminal connector which will maintain good electrical contact indefinitely. It is a further object of this invention to provide a terminal connecting block which will permit a number of connections to be made on one terminal. Still another object of this invention is to provide an electrical connector that is capable of positively engaging a conductor for long periods of time, even under vibration, without deteriorating as a result of metal fatigue in the connector. Other objects will appear hereinafter.

Briefly, the objects of this invention are attained by providing a novel electrical connector which may be embedded in a base member of a suitable electrical insulating material. At least one, and preferably several upright or vertically disposed helical connectors may be embedded in the base member. The helical connectors are in the form of a continuous spiral of a suitable resilient conducting mate-rial which forms a plurality of closely spaced adjacent compact coils. Each coil is bounded on each surface thereof by angularly disposed planar surfaces rather than circular or arcuate surfaces. Thus the cross-sectional shape taken through the metal strip forming each coil may be polygonal; such as, for example, triangular, square, rectilinear or hexagonal.

The invention will be more particularly described with reference to the accompanying drawings wherein:

FIGURE 1 is a side elevational view of a helical connector constructed according to this invention.

FIGURE 2 is a top plan view of a terminal connecting block having connectors such as shown in FIG. I mounted therein.

FIGURE 3 is a cross-sectional view taken along line 3-3 of FiGURE 2, and shows how a terminal connector of the type shown in FIGURE 1 may be embedded in a base member. This figure also shows an insulated electrical conductor connected to the terminal connector.

FIGURES 4 and 5 are cross-sectional views of helical connectors of Varying construction.

FIGURES 6 to 9 are side elevational views of connectors of varying structures.

FIGURE 10 is a cross-sectional view of another type of helical connector in combination with an insulated electrical conductor.

Referring more particularly to the drawings, there is shown a helical connector 20 formed by shaping a strip of resilient material into a continuously ascending spiral thereby providing a plurality of compact coils 2E. The cross-sectional shape of the strip from which the coil is formed must be angular.

While the adjacent coils of the connector may be contiguous-i.e., so compact that they are actually in contact or touching one anotherit is preferred, as shown in FIGURE 3, that a small space 22 separate the adjacent coils 21. The space 22 should not be larger than the diameter of the conductor wire which is to be connected thereto.

The number of coils in each helical connector is not particularly critical and is largely a matter of choice. The actual number will be dictated by the number of connections which it is desired to make on each connector. Generally, the helical connectors of this invention will be comprised of at least four coils.

The connector may be constructed of any suitable resilient conducting material and is preferably a metal such as Phosphor-bronze, beryllium-copper, etc. It is preferred that the metal be plated with tin to prevent corrosion of the connector.

It is essential that the configuration of the cross-sectional shape of each coil in the helical connectors of this invention be bounded by surfaces that are angularly disposed to one another rather than circular. By angular cross-section, it is meant that the periphery of the crosssection meets in at least one well defined point to form an angle. Thus, the surface of each coil contains at least two longitudinal surfaces which meet at an abrupt conthe conductor.

verging sharp edge on the surface of the coils in the connector. These longitudinal surfaces will usually be fiat but are not necessarily so. When the surfaces are flat, the cross-sectional configuration of each coil is polygonal as illustrated in FIGURES l, 3, 4, 5 and 10.

In a preferred embodiment 'of this invention, as shown in FIGURES 1 and 3, the individual coils 21 in the connectors have cross-sections 23 in the shape of isosceles 7 triangles, the base 24 of the cross-section facing the inside of the helical connector forming a smooth surface on the inside of the connector. Since the apex 25 of the cross-section of each coil faces outwardly, there is provided a V-shaped opening between the adjacent coils which facilitates the insertion of a conductor.

Helical connectors constructed according to this invention may be used in various environments. In a preferred embodiment, at least one helical connector is embedded in a suitable base member to provide .a terminal connecting block. In practice, where it is desired to provide a large number of connections, such as between telephone subscribers in an apartment or oflice building and a central exchange, it is preferred to provide a plurality of helical connectors in a base member 26 as shown in FIGURE 2. For convenience, the plurality ofconnectors are generally arranged in parallel rows.

As shown in FIGURE 3, the helical connectors 20 may be embedded in a base member 26 of a suitable electrical insulating material such as a phenol-formaldehyde resin or a polyvinyl resin. At least one, and preferably two or more, coils are disposed below the uppermost surface of .the base member and are thus embedded therein. It is preferred to mold the helical connectors directly into the base member. However, the base member may be formed by molding in threaded cavities and subsequently screwing the helical connectors into the cavities.

As illustrated in FIGURE 3, connection of an insulated electrical conductor 27 may be easily accomplished by forcing the insulated conductor 27 directly between the faces of two opposing coils 21.21. The electrical insulation 28 is thereby automatically and instantaneous- 1y stripped or pierced at the point of contact between the edges of the coils and the conductor. The abrupt edges 23aof the coils 21-.21 make an electrical contact with the bare conductor wire 29 at the point where the insulation 28 was stripped. This is insured by having adjacent coils spaced from one another a distance not greater than the diameter of the conductor and preferably, a distance less than that equal to the diameter of Since .the insulation on the insulated conductoris pierced only at the point of contact with the edges of the coils, there are no large areas of bare conductor exposed .or showing If desired, the coils may be in contact with each other with the abrupt edge 23a of each coil in contact with the corresponding edge of the adjacent coil. It has been found that the abrupt edge 23a on the coil makes a more effective electrical contact than is possible to attain by conventional connectors such as those wherein a conductor is securedto a terminal post by means of a nut or where contact is provided between two curved surfaces. Moreover, the tension due to the. elasticity of the helical conductor in combination withthe abrupt edges of-the coil which are in contact withthe conductor insures that the contact is positive and will not-weaken due to metal fatigue after long periods of use, even under continuous vibration. The abrupt edges of the coils 21 are very effective in removing the insulation from the conductor when the latter is forced into a positionbetween the adjacent close- 1y spaced coils.

A large number of connections maybe made on each helical connector. Several conductors may be inserted between each set of opposing faces of the coils which extend above the base. Thus, in a terminal connecting block in which ten coils of each helicalconnector extend above the block, there will be nine sets of opposing faces of the coils. Since three or more conductors may be inserted between each set of opposing faces, it can be seen that twenty-seven or more connections may be made on each connector. Since a plurality of helical connectors are present in each terminal connecting block, the number of connections which may be made by means of one block is greatly increased over connecting blocks previously known to the art.

Although, as previously described, it is preferred that the cross-section 23 of each coil be triangular in shape, other configurations may also be employed in accordance with this invention. FIGURE 4 shows coils 21' having square cross-sections 23'. FIGURE 5 shows coils 21" having hexagonal cross-sections 23" or rectangular cross-sections wherein the outer edges are bevelled as at 23a.

- FIGURES 6 to 8 illustrate structural variations of the connector of FIGURES l and 3. In FIGURE 6, there is a stud 30 extending down through the middle of the connector 20 and into the base member 26. At the bottom of the stud 30 there is a base 31 which is embedded in the insulating material which comprises the base member 26. At the top of the stud 30, there is a cap 32 which covers the top of the connector 20. The stud imparts rigidity to the helical connector and limits the length to which the spiral connector may be pulled apart or otherwise distorted by an installer and also anchors the connector more firmly in base member 26. The cap 32 serves the further purpose of preventing foreign matter from falling into the center of the connector.

In FIGURE 7, a tang or prong 33 extends from the top end of the connector 20a down through the middle and is embedded in the base member 26. FIGURE 8 shows a tang 33 extending from the top of the connector 20b down the outside thereof and embedded in the base member 26. Both tangs 33 and 33' are for the purpose of imparting rigidity to the helical connector, holding the spiral to a fixed overall length and to anchor it more securely in the base member. It will be noted that each of the embodiments of FIGS. 6, 7 and 8 includes means. for controlling the overall length of the spiral connector. This control is achieved either by limiting the length to which the connector may be expanded or by rigidly holding the coil to a fixed overall length. InFIGURE 9, a threaded stud, 34 is secured, as by soldering, to the bottom of the connector 200. A nut 35 is threadably mounted on the stud 34. This type of electrical connector is particularly well suited for use with a peg board in the electronics field. The stud 34 may be inserted through a hole in the peg board and the nut 35 threaded onto the stud on the opposite side of the board thereby securing the connector to the peg board. As can be readily appreciated, the connector may thus be easily and quickly moved from one position to another as desired.

FIGURE 10 illustrates another preferred embodiment of an electrical connector in combination with an insulated electrical conductor. Each of the individual coils 21' of the helical connector 20" has a cross-sectional configuration 23" which comprises a partially planar surface 23b on both the top and bottom sides of the coil. The planar surface 23b on one side of the coil is interrupted by a projecting peak 23c, the apex of the peak 230 defining an abrupt edge 23:1. The planar surface on the other side of the coil is interrupted by a curved indentation 232. The helical connector is constructed so that the peak 230 on one coil registers with the curved indentation 236 on the adjacent "coil. When an insulated electrical conductor 27 is forced between two opposing coils, the electrical insulation 28 is pierced at the point of contact with the peak 230, thereby establishing electrical contact between the conductor wire 2 and the connector 20*". As is apparent from FIGURE 10, the insulated electrical conductor is criniped between the peak 230 and the indentation 23a. This has the effect of securely holding the conductor wire. The opposing planar surface portions of the coils which are in contact with the insulated electrical conductor distribute any force which may be exerted on the top of the spring over a Wide area, thereby avoiding any possibility of the conductor being severed at the point of contact with the peak 23c through pressure exerted on the top of the spring.

Many variations and related embodiments other than those described above will be apparent to those skilled in the art. For example, a terminal connecting block may have the helical connectors extending all the way through the block so that connections may be made on either side. Moreover, the helical connectors constructed according to this invention may be used in structures other than the terminal blocks previously described-e.g., they may be used in connecting one 'or more insulated conductors to a bolt, binding post or other electrical outletv This application is a division of my copending application Serial No. 190,173, filed April 25, 1962, now Patent No. 3,131,015; which, in turn, is a continuation-in-part of my application Serial No. 72,670, filed November 30, 1960, now abandoned.

I claim:

1. A helical electrical connector comprising a continuous spiral of a strip of resilient electrical conducting material forming a plurality of compact coils having a common central axis, said strip having a generally triangular cross-sectional shape, one apex of said of said triangular shape pointing radially away from said central axis, two apices of said triangular shape lying opposite and aligned with similar apices of adjacent said coils; whereby the insulation on an insulated wire conductor is pierced and contact is achieved at separate points on a wire conductor which is inserted between two adjacent coils of said conductor.

2. The connector of claim 1 having means controlling the overall length of said spiral.

References Qitetl in the file of this patent UNITED STATES PATENTS 941,893 Steinberger Nov. 30, 1909 1,933,555 Jasper Nov. '7, 1933 2,951,109 Bollmeier et 'al. Aug. 30, 1960 3,066,274 Ellis Nov. 27, 1962 FOREIGN PATENTS 635,943 Great Britain Apr. 19, 1950 

1. A HELICAL ELECTRICAL CONNECTOR COMPRISING A CONTINUOUS SPIRAL OF A STRIP OF RESILIENT ELECTRICAL CONDUCTING MATERIAL FORMING A PLURALITY OF COMPACT COILS HAVING A COMMON CENTRAL AXIS, SAID STRIP HAVING A GENERALLY TRIANGULAR CROSS-SECTIONAL SHAPE, ONE APEX OF SAID OF SAID TRIANGULAR SHAPE POINTING RADIALLY AWAY FROM SAID CENTRAL AXIS, TWO APICES OF SAID TRIANGULAR SHAPE LYING OPPOSITE AND ALIGNED WITH SIMILAR APICES OF ADJACENT SAID COILS; WHEREBY THE INSULATION ON AN INSULATED WIRE CONDUCTOR IS PIERCED AND CONTACT IS ACHIEVED AT SEPARATE POINTS ON A WIRE CONDUCTOR WHICH IS INSERTED BETWEEN TWO ADJACENT COILS OF SAID CONDUCTOR. 